Soil stabilization techniques such as helical plate bearing anchors, mini-piles and micro-piles are known. For example, helical plate bearing anchors are mounted on steel bar shafts and pipe shafts with plate helices that are drilled into soil and used as tension, compression and lateral force resisting members. These types of anchors may be mounted to hollow shafts to provide a channel for injecting solidifying material into the subsurface after drilling is completed. For example, hollow drill rods and drill shafts are used with grout in forming tiebacks, mini-piles, rock anchors, soil nails and other micro-pile uses.
Further, various types of auger tools are used for excavating holes. This type of tool may have a disposable drill head. Flight augers have continuous helices along the length of the shaft. Because of the expense of this type of auger, the auger is generally removed from a drill hole and not left in place, the drill hole subsequently filled with solidifying material to form a mini-pile.
In U.S. Pat. No. 5,575,593 to Raaf, a method and apparatus for installing a helical pier with pressurized grouting is disclosed. An anchor having helices is rotated into the ground. The helical anchor is hollow and includes multiple perforated holes along its length and about its perimeter. After the anchor is drilled into the ground, pressurized grout is injected therein and forced out the perforated holes.
In U.S. Pat. No. 4,009,582 to LeCorgne, a method is described for forming a caseless concrete pile using a hollow pipe, a connector and a tubular driving mandrel. In U.S. Pat. No. 3,512,366 to Turzillo, a hollow auger for drilling holes is disclosed. The auger described in the Turzillo patent is withdrawn from the hole leaving a steel rod with drill bit in place with concrete thereafter poured for forming a concrete pier.
In U.S. Pat. Nos. 4,492,493 and 4,756,129 to Webb and U.S. Pat. No. 3,115,226 to Thompson, Jr. different types of ground anchors and apparatus are described. Also, U.S. Pat. No. 4,998,849 to Summers, U.S. Pat. No. 3,961,671 to Adams et al. and U.S. Pat. No. 4,678,373 to Langenbach, Jr. disclose different types of driving apparatus and methods of shoring structures.
Other varieties of ground anchor devices used for soil stabilization have been described. In particular, U.S. Pat. No. 6,722,821 to Perko et al. and U.S. Pat. Nos. 5,904,447, 5,919,005 and 5,934,836 to Rupiper et al. disclose recent anchor devices using helical piers for stabilizing soil and for securing building foundations and other structures.
The above described and other known soil stabilization and anchoring techniques include either pumping a solidifying material under pressure through a hollow drilling apparatus and out holes contained therein once the drilling apparatus has been advanced into the ground subsurface, or alternatively, withdrawing the drilling apparatus and thereafter pumping a solidifying material under pressure into the space created by the drilling apparatus. Unfortunately, such post-drilling operation techniques leave voids both within the solidifying material and between the solidifying material and soil with resulting loss of soil stabilization and resistance to displacement.
Accordingly, there is still a continuing need for improved system designs that result in voidless solidifying material placement. In presenting a novel way to deliver the solidifying material during the drilling process, the present invention fulfills this need and further provides related advantages.